The present invention relates to a stretching machine for stretching a stretchable long sheet-like member such as a polyethylene film (including a slitted film), a net, woven fabric and non-woven fabric, in the direction of width.
There is a known stretching machine in Japanese Patent Publication No. 57-30056, in which there are a pair of support plates, an inlet side for a long sheet-like member, and an outlet side, with the space between the plates increasing from the inlet to the outlet side. A stretching pulley and a circulating belt are mounted on the support plate so as to stretch the sheet-like member in the direction of width by holding the sheet-like member between the pulley and the belt. To heat the sheet-like member to a temperature suitable for stretching, a spaced apart infrared heater or hot air is used.
One end of the support plate is connected to a spline shaft at the inlet side for, and the other end at the outlet side being connected to the spline shaft, the one being movable in a lateral direction.
In the stretching machine, there is a disadvantage of a large heat loss because radiation heat or hot air goes away after the stretchable sheet-like member which is heated to a certain temperature owing to non-collection thereof. In addition, when the infrared heater is used, there is a disadvantage that discontinuation of the sheet-like member would melt the member itself so as to damage the quality of products owing to difficulty in temperature control of radiation heat. In the above stretching machine, both the support plates, accessibly connected with spline shafts, make the spreading size of the sheet-like member adjustable, but the stationary remote infrared heater and nozzle make it impossible to heat all the stretched portions of the sheet-like member to a uniform temperature.
In the above stretching machine, when the sheet-like member is heated with radiation heat or hot air during stretching of the sheet-like member, the stretching pulleys and a circulating belt are heated at the same time. The sheet-like member is heated once, but the stretching pulleys and belt are continuously heated to a temperature the same as that of the sheet-like member or above. Thus, the sheet-like member held between the pulley and the belt becomes crinkled, and at worst, the crinkled portion is melted to stick to the stretching pulley and belt so as to be damaged, and is wound to pulleys with which the belt is engaged. There is a disadvantage that the life of the belt itself is remarkably shortened owing to heat damage.
In the stretching machine described above, it lacks clarity how to adjust and determine an angle between the support plates; thus, it is necessary to improve a method of adjusting stretch width or stretch ratio of a stretchable sheet-like member or a film.